Recently, software has been run in virtualized hardware environments called virtual machines (VMs). A VM may have a virtual disk image that functions as a virtual hard drive. That is, the VM image (VMI) is a file that a virtualization layer may use to boot a VM, may contain a guest operating system and other software to run within the operating system. A VMI may be duplicated and each duplicate may serve as the virtual disk for its own VM instance. In other words, there may be many VMs running respective copies of a same VMI. Therefore, these VMs are likely running at least some of the same software found on the original VMI.
A problem, not previously appreciated, is that there has been no way to conveniently understand which VMs currently have which pieces of software, which hosts of VMs are linked to which source code files (of applications thereon), and so forth. While it may be possible to manually examine a VMI and identify software installed therein, there is no systematic way to accomplish this in an environment where software is often recompiled and reinstalled on VMIs, and where VMs using the VMIs are constantly deployed, redeployed, deleted, instantiated, etc. For example, in a cloud hosting environment or a data center, in response to current network of computing conditions, or in response to changing user requirements, new VM instances (having specific target software) may be created and started, old VM instances may be shut down, and/or VM instances (and their VMIs) may be moved from one host to another host. Persons interested in a particular software application may not be able to quickly assess exactly which hosts are running which pieces of the software. Similarly, persons managing the cloud or data center may, for diagnostic or performance reasons, desire to know which software is on which hosts.
Moreover, detailed information about the software on VMs may be limited. For example, it may at times be desirable to know exactly which source code files contributed to the software installed on a VM/VMI. Where VMs have been employed, there has been no way to quickly obtain answers to questions such as “which hosts currently have VMs with software built from source code file F?”, or “which source code files contributed to the VM-based software on host H?”
Techniques related to tracking VM-software lineages are discussed below.